1. Technical Field of the Invention
The present invention relates generally to an electrically motorized wheel assembly in which an electric motor is located eccentrically from an axle of a wheel for use in, for example, automotive vehicles, electrically-powered chairs, or electrically-powered carriers of robots, and more particularly to such an electrically motorized wheel assembly equipped with a protective cover.
2. Background Art
There are known electrically-powered carriers such as electric vehicles equipped with at least one pair of right and left motorized wheels each of which is driven by an electric motor. Motorized wheels of this type have the advantage that a differential gear or a long axle is not needed, thereby resulting in decreases in total weight of the carrier and inertia mass of rotating parts or a simplified structure of the carrier as compared with carriers in which a single electric motor is used to drive a pair of right and left wheels.
Japanese Patent First Publication No. 2004-90822 teaches an eccentric motor layout motorized wheel in which an output shaft of an electric motor is located eccentrically from an axle of the wheel. This structure has the advantage of increasing the degree of freedom of layout of the electric motor.
The eccentric motor layout motorized wheel requires the need for installation of a gear mechanism therewithin in order to transmit torque from the motor to the axle. In the case of use in automotive vehicles, the motorized wheel is sometimes placed in severe environments such as dust or muddy water conditions, which leads to a greater concern about an increase in wear of the parts, loss of torque transmission, or mechanical noise.
The above problem usually underlies all types of motorized wheels, but however, the eccentric motor layout motorized wheel has the output shaft of the motor not located coaxially with the axle and, thus, encounters a difficulty in protecting the gear mechanism from dust without mechanical interference with the motor and the axle. Of course, it is also difficult to employ a large-sized, complex sealing mechanism or a high-friction sealing mechanism.